In order to be able to meet the increasingly stringent statutory environmental protection requirements such as LEV in the USA or EU6 or EU7 in the European Union, the exhaust gases of an internal combustion engine, for example a spark-ignition or diesel engine, used to power motor vehicles, may be treated so that the pollutant emissions of the internal combustion engine remain below prescribed maximum limits. In the case of spark-ignition engines, for example, catalytic reactors are used as exhaust gas aftertreatment units which, by using catalytic materials that increase the speed of specific reactions, ensure the oxidation of hydrocarbons (HC) and carbon monoxide (CO), for example. Oxidation of the unburned hydrocarbons and carbon monoxide relies, in particular, on the provision of an oxidation catalytic converter in the exhaust gas flow.
The ageing of catalytic converters used as exhaust gas aftertreatment units constitutes a common problem. These catalytic converters have a coating of noble metals, which is consumed as the number of operating hours of the engine and/or catalytic converter increases. In order to be able to meet the aforementioned environmental protection requirements even after a high number of operating hours, the catalytic converters are furnished with excess noble metal, which particularly in the context of an overall increase in the cost of raw materials makes manufacture of the catalytic converters more expensive and does not really solve the problem of ageing but merely defers it.
The inventors herein have recognized the above issues and have developed a ducting system so that the relevant environmental protection requirements can be met by the catalytic converters used for exhaust gas aftertreatment even after a high number of operating hours, without needing to provide an excess of noble metal. In this way, the problem of ageing of the catalytic converters may be counteracted.
Accordingly, a ducting system for feeding air and exhaust gases to an internal combustion engine and for discharging the exhaust gases produced by the internal combustion engine from the internal combustion engine is provided. In one embodiment, the ducting system comprises a feed duct for feeding the air and exhaust gases to the internal combustion engine, a discharge duct for discharging the exhaust gases produced by the internal combustion engine from the internal combustion engine, in which one or more exhaust gas aftertreatment units are arranged for aftertreatment of the exhaust gases, and a heating device arranged in the feed duct. The heating device is configured to perform a heating process for preheating the air that is fed to the internal combustion engine. A duration of the heating process and/or heat output given off by the heating device is controlled as a function of a variable approximately representing a state of ageing of at least one of the one or more exhaust gas treatment units.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.